Image motion extraction of structures using computer vision techniques: A comparative study
Journal
Sensors
Journal Volume
21
Journal Issue
18
Date Issued
2021
Author(s)
Abstract
Vibrational measurements play an important role for structural health monitoring, e.g., modal extraction and damage diagnosis. Moreover, conditions of civil structures can be mostly assessed by displacement responses. However, installing displacement transducers between the ground and floors in real?world buildings is unrealistic due to lack of reference points and structural scales and complexity. Alternatively, structural displacements can be acquired using computer vision?based motion extraction techniques. These extracted motions not only provide vibrational responses but are also useful for identifying the modal properties. In this study, three methods, including the optical flow with the Lucas–Kanade method, the digital image correlation (DIC) with bilinear interpolation, and the in?plane phase?based motion magnification using the Riesz pyramid, are introduced and experimentally verified using a four?story steel?frame building with a commercially available camera. First, the three displacement acquiring methods are introduced in detail. Next, the displacements are experimentally obtained from these methods and compared to those sensed from linear variable displacement transducers. Moreover, these displacement responses are converted into modal properties by system identification. As seen in the experimental results, the DIC method has the lowest average root mean squared error (RMSE) of 1.2371 mm among these three methods. Although the phase?based motion magnification method has a larger RMSE of 1.4132 mm due to variations in edge detection, this method is capable of providing full-field mode shapes over the building. ? 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Subjects
Bilinear interpolation
Digital image correlation
Modal property extraction
Optical flow
Phase?based motion magnification
Riesz pyramid
Edge detection
Extraction
Mean square error
Optical correlation
Optical flows
Structural health monitoring
Transducers
Computer vision techniques
D. digital image correlation (DIC)
Displacement response
Displacement transducer
Linear variable displacement transducers
Root mean squared errors
Structural displacement
Computer vision
computer
motion
Computers
Motion
SDGs
Type
journal article